"ED may be a sign of subclinical cardiovascular dysfunction," said Blaha.

Experts have long observed that impotence is associated with poor cardiovascular health, but it was thought that obesity, high blood pressure and diabetes were some of the reasons why.

This study found that impotence on its own is a significant risk factor.

"In addition, this signal for increased risk is independent of depression and medication usage, said Blaha. That appears to negate theories that depression or its treatment might explain any link between impotence and heart disease.

Study participants were enrolled in the Multi-Ethnic Study of Atherosclerosis, conducted in several U.S. cities. Over four years, 115 men had a serious heart problem, such as heart attack, stroke or cardiac arrest.

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The investigators determined that just over 6 percent of men with ED experienced such an event, compared with just under 3 percent of sexually healthy men.

So what should an impotent man do?

Blaha suggested a visit to a doctor or a preventive cardiologist. "In some cases, these men need screening for early cardiovascular disease," he said.

"Many men at risk for cardiovascular disease seek medical care not for management of risk factors, but for their ED. Our study is an alert that such patients need a thorough cardiovascular evaluation in addition to their treatment for ED," Blaha said

Dr. Richard Becker, an American Heart Association spokesman, said the study results need confirmation. Still, the strength of the findings were "striking," he said.

"Health care providers should consider including ED as a component of assessing cardiovascular risk among middle-aged men," said Becker, a professor of medicine at the University of Cincinnati who was not involved with the study.

"While there are effective treatments for ED, one must never overlook an opportunity to ask a simple question: 'Why?' In addition, men should be aware of the potential implications of ED and inform their provider," Becker said.